Being sessile, plants are constantly exposed to changes in temperature and other abiotic stress factors. The temperature stress experienced by plants can be classified into three types: those occurring at (a) temperature below freezing (b) low temperature above freezing and (c) high temperature. The plants must adapt to them in other ways. The biological substances that are deeply related to these stresses, such as heat shock proteins, glycine betaine as a compatible solute, membrane lipids etc.and also detoxifiers of active oxygen species, contribute to temperature stress tolerance in plants. Rapid advances in Molecular Genetic approaches have enabled genes to be cloned, both from prokaryotes and directly from plants themselves, that are thought to provide the key to the mechanism of temperature adaptation (Iba et al., 2002).
The accumulation of heat shock proteins under the control of heat stress transcription factors is assumed to play a central role in the heat stress response and in acquired thermotolerance in plants (Kotak et al., 2007). The pattern of protein synthesis during cold acclimation is very dissimilar to the heat shock proteins in many ways. Different low temperature stress proteins, such as Anti-freeze proteins or thermal hysteresis proteins (THPs) and cold shock domain proteins etc. are accumulated in plant cell and are frequently correlated with enhanced cold tolerance ( Guy, 1999).
The heat stress-induced dehydrin proteins (DHNs) expression and their relationship with the water relations of sugarcane (Saccharum officinarum L.) leaves were studied to investigate the adaptation to heat stress in plants (Wahid and Close, 2007). In order to get an in vitro evidence of Hsc70 functioning as a molecular chaperone during cold stress, a cold-inducible spinach cytosolic Hsc70 was subcloned into a protein expression vector and the recombinant protein was expressed in bacterial cells. Results suggest that the molecular chaperone Hsc70 may have a functional role in plants during low temperature stress (Zhang and Guy, 2006). To analyze the least and most strongly interacting stress with Hsps and Hsfs, a transcriptional profiling of Arabidopsis Hsps and Hsfs has been done (Swindell et al., 2007).
As plants receive complex of stress factors together, therefore in future research, emphasis should be placed on such cases where tolerance is attempted to different stress factors simultaneously by employing sophisticated techniques.